Network resources, such as web servers hosting web sites, are typically accessible over the Internet by network addresses. For example, in accordance with the Internet Protocol (IP) version four, commonly referred to as IPv4, a network address at which a network resource is accessible is given as a.b.c.d, where each of a, b, c, and d is an integer between 0 and 255. As another example, in accordance with the IP version six, commonly referred to as IPv6, a network address is given as a:b:c:d:e:f:g:h, where each of a, b, c, d, e, f, g, and h is a hexadecimal number from 0x0000 to 0xFFFF. A given network resource may be accessible by an IPv4 address, by one or more IPv6 addresses, or by both an IPv4 address and one or more IPv6 addresses.
Because users have difficulty remembering network addresses, a domain name system (DNS) has been developed in which more easily remembered network names are associated with network resources. A given network resource may have a network name specified as “name” separated from each of a prefix “www” and a suffix “com” by a period (“.”), for instance. When a user enters a network name by which a network resource is identified, such as within a web browser computer program, a DNS server is sent the network name to resolve the name into the actual network address of the resource. Thus, the network name may be resolved to an IPv4 network address a.b.c.d, and/or one or more IPv6 network addresses each having the form a:b:c:d:e:f:g:h.
Historically, network resources were accessible over the Internet via IPv4 network addresses only. However, for a variety of reasons, including primarily the concern that the number of unique IPv4 network addresses was running out, addressing is being slowly transmitioned to IPv6 network addresses, such that network resources will each ultimately become accessible by one or more IPv6 network addresses. During the transmition period, situations can thus occur in which a network resource may be accessible by an IPv4 address, one or more IPv6 addresses, or both an IPv4 address and one or more IPv6 addresses.
However, IPv4 DNS servers can only provide the IPv4 addresses of network resources. By comparison, IPv6 DNS servers primarily just provide the IPv6 addresses of network resources, although IPv6 DNS servers can in some instances provide IPv4 addresses as well. Therefore, when a network name is provided, there is an issue as to which DNS servers—IPv4 or IPv6—should be inquired to provide a network address, and in what order, especially in relation to a computing device that is capable of using both IPv4 and IPv6 addresses.